Telephone-transmitter.



J. c. R. PALMER. TELEPHONE TRANSMITTER. APPLICATION YI'LED APR. 15, 1912Patented 'Mar'. 23; 11915.

Fig. 2. I

Wbnesses;

MVenZc? UNITED STATES PATENT OFFICE.

JOEL C. B. PALMER, OF BROOKLYN, NEW YORK, ASSIGNOR TO WESTERN ELECTRICCOMPANY, OF NEW YORK, N. Y., A CORPORATION OF ILLINOIS.

TELEPHONE-TRANSMITTER.

Specification of Letters Patent.

Patented Mar. 23, 1915.

Application filed April 15, 1912. Serial No. 690,844.

To all whom it may concern:

Be it known that I, Jonn C. R. PALMER, citizen of the United States,residing at Brooklyn, in the county of Kings and State of New York, haveinvented a certain new and useful Improvement in Telephone-Transmitters, of which the following is a full, clear, concise, andexact description.

This invention relates to telephone transmitters, and has for its objectto provide a transmitter structure in which the detrimental effect, dueto an inactive mass of granular carbon or other comminuted material, iseliminated, and the transmitting qualities otherwise improved.

In the commonly known type of SOlldback transmitter employing comminutedmaterial as a resistance-varying medium,

there has been a portion of the comminuted resistance-varying materialwhich is practically inactive due to the fact that it has settled in thebase of the button chamber and is very slightly agitated by the movementof the electrodes. This mass is, therefore, of relatively low resistanceand forms a shunt to the path which is actually subject to variation. Inaccordance with this invention the detrimental feature of this shunt isobviated by so shaping the electrode chamber and adjusting the sizes ofthe electrodes that the percentage of the inactive material in thebutton is very small compared to the total amount, and is restricted toan area such that no portion of it is in contact with one of theelectrodes, and any current which has a path through such inact amaterial must pass also through the material undergoing the maximumagitation. The structure preferably employed for accomplishing thisresult comprises a chamber, the wall of which is sloped or tapered toform the frustum of a cone and has located in the smaller end thereof anelectrode of the same diameter as said smaller end. Located in theopposite side of said chamber is a second electrode having a larger areathan the area of the first electrode exposed to the comminuted materialin the chamber, the exposed area of the second electrode being sorelated to the chamber that the small amount of inactive material isrestricted to a small area at the margin of said larger electrode, wlf2h area is a greater distance from the smaller electrode than is anypoint on the exposed surface of the ele "'ode of larger area. The largerelectrode may be formed of rigid material and secured to a flexiblediaphragm of insulating material, or said electrode may be formed offlexible metal,

such as gold, of sufficient area to cover-the front of the chamber andhave its inner surface near the margin thereof covered with insulatingmaterial to expose only a portion thereof to the comminuted material,the exposed area in both forms being practically the same. Any advantagein either of the structures, however, is probably in favor of theelectrode of rigid material inasmuch as in the case of the electrode ofrigid material the agitation is substantially uniform throughout thesurface of said electrode, whereas in the use of the flexible electrodethe maximum disturbance occurs in the central portion of the chamber andthe amount of action decreases rapidly from the center outwardly towardthe margin of the electrode.

Another feature of this invention relates to a structural detail wherebythe minimum number of parts are used for constructing the button, andthis feature consists in hollowing out the metal button supporting theelectrodes to the shape of the chamber desired and applying a coating ofsuitable insulating material thereto, thus avoiding the use of aspecially formed insulating member for the wall of the chamber, theresult being to both cheapen and improve the structure.

In the drawings in which this invention is illustrated with electrodesof rigid material-Figure 1 is a sectional elevation of a transmitterembodying the invention; and Fig. 2 is a view of the transmitter partsof the invention separated and in position for assembly.

In Fig. 1 of the drawings, 5 designates the usual mouthpiece secured ina screwthreaded opening in a face plate 6. Secured to the rear of thisface plate 6 is a metal bridge piece 7 provided with a centrally locatedaperture 8 through which is a clamping ring 12 adapted to press againstof the smaller electrode 24 to the coma washer 13 of insulating materialsurminuted material beyond the margin of the rounding said block 9 andfitted into a relarger electrode 23 is greater than the discess 14 ofthe inner face of the bridge piece. tance from any point of said smallerelec- The chamber for the electrodes and comtrode 24 to the larger ormovable electrode 70 minuted material is as follows: A metal cup 23.Thus it is evident that any current hav- 18 having a stem 19 thereonwhich extends ing a path through the comparatively inthrough an openingin the block 9 is proactive material beyond the margin of the vided witha sloping or tapering inner wall larger electrode must also pass throughthe 20 which is the shape of the frustum of a active material betweenthe two electrodes, cone. The cup is provided with exterior thusundergoing the maximum change and screw-threads adapted to receive ametal avoiding the shunting of the active path. clamping ring 21 betweenwhich and the he feature of applying the insulating edge of the cup isclamped a mica diamaterial directly to the wall of the metal 15.' phragm22 to which is secured a carbon elec chamber has advantages over priorforms of trode button 23. Located upon the opposite buttons in that itavoids the use of extra side of the cup is a second carbon electrode ple parts ch s insulating strips which 24 secured to a metal disk 25having a were necessary formerly when the chamber screw-threaded stem 26engaging a screwwas formed In metal and the extra parts 20 threadedaperture in the stem 19 of the cup necessary for retaining theinsulating strips 18. As shown, the electrode 24 is the same d mp tingthe terminal connections to diameter as the smaller diameter of the cupthe electrodes. wall 20, and is fitted into said cup wall so I 1mm thatthe exposed face of the said electrode A ph ne transmitter having an 25i fl h ith th d f th cup 11 Th electrode chamber with a tapered we 1, anelectrode 23 is larger in diameter than the electrode at one end of Saidchamber, a electrode 24 but not so large as the largest d electrode rgthan the first at the o diameter of the conical chamber. The wall Poslteend of Said h mber and having a iiiof th h b i t d as h w t 15 ameterless than the largest diameter of 80 with an insulating compound of anysui t- Sald chamberable form which is applied in a liquid state Atelephone transmitter a ing an and subsequently hardened upon the wall.t ode chamber with a tapered wall, a S d t th i di k 23 i a t d 30 thstationary electrode located at the smaller outer end of which isprovided with an insuend o id m r, a closure for the larger 35 l ti k b31 i a t, ith a i end of said chamber, and an electrode car- 0 dentation32 in a metal diaphragm 33 restried by said closure having an arealarger ing against a strip 34 of insulation whi h than the area of saidstationary electrode bears against the inner face of the face plate dmaller than the total area of said earing against a collar 35 on thestud o r 40 30 is a damping spring 38 the outer end of 3. A telephonetransmitter having an which is attached to the inner face of theelectrode chamber with a tapered wall, combridge piece 7. The dampingspring 38 is minuted material in said chamber,- a stainsulated from thebridge piece 7 but is in tionary electrode located at the smaller endelectrical connection with a terminal block of said chamber a closurefor the larger end 45 40 located upon the opposite face of said of saidchamber, said closure presenting a bridg'e iece 7 but insulatedtherefrom The central conducting surface and a peripheral block 0constitutes the terminal of the non-conducting surface to said commmutedtransmitter with which the movable elecmaterial, said conducting surfacehaving an trode 23 is connected. The terminal for area greater than thearea of said stationary 0 the stationary electrode 24, if thetransmitelectrode.

ter is to be used as an insulated transmitter, 4. A telephonetransmitter havin an is connected with a binding screw 43 securedelectrode chamber the shape of the frustum in the member 10 or if theinstrument is to of a cone, an electrode of the same diamebe grounded, aground Wire 44 will be led ter as the smaller end of said chamber se- 55from the binding screw 43 along the bridge cured therein, and a movableelectrode of piece 7 and attached at its opposite end to rigid materiallocated upon the opposite a clamping screw 45. In this case, a bell sideof said chamber, said movable electrode 48 inclosing the transmitterparts and being of greater diameter than the firstadapted for connectionwith a desk stand mentioned electrode and of less diameter 6 or othersuitable subscriber set. will be than the largest diameter of saidchamber. grounded. 5. A telephone transmitter having an By referring tothe drawing it will be electrode chamber with a, tapered wall, notedthat the relative sizes of the two eleccomminuted material in saidchamber, an trodes 23 and 24 and the slope of the wall electrode at thesmaller end of said cham- 6 20 is such that the distance from any pointher, a second electrode located in the opposite end of said chamber,said second electrode having exposed to the comminuted material in thechamber an area greater than the area of said first-mentioned electrodebut less than the area of the larger end of said chamber.

6. A telephone transmitter having an electrode chamber with a taperedside wall, comminuted material in said chamber, an electrode located atthe smaller end of said chamber, a movable electrode of larger diameterat the'opposite end of said chamber, said larger diameter electrodehaving a conductive area exposed to said comminuted material of lessdiameter than the largest diameter of said electrode chamber.

7. A telephone transmitter having an electrode chamber with a taperedwall, comminuted material in said chamber, a sta- JOEL C. R. PALMER.

\Vitnesses:

G. M. CAMPBELL, W. F.- HOFFMAN.

